a) giả sử X=a/m ,Y=b/m (a,b,m thuộc Z ,m>0) va x<y. Hãy chứng tỏ rằng nếu chọn Z=a+b/2 thì ta có x<z<y b) cho hai số hữu tỉ a/b và c/d (b>0, d>0) . Chứng minh rằng nếu a/b > c/d thì ad> bc và đảo lại nếu ad> bc thì a/b > c/d. Giúp mik với ạ!!!!

Đề: tìm x trong các tỉ lệ thức sau!

dich ra nếu tiện thì trả lời hộ tui nha , hơi mờ nhưng mong các bạn nhìn tạm

HELLLLLLLLLLLLLLLLLPPPPPPPPPPPPPPPP MMMMMMEEEEEEEE!!!!!

x(x^2+x+1)-x^2(x+1)-x+5 x(2x+1)-x^2(x+2)-x^3-x+3 4(6-x)+x^2(2+3x)-x(5x-4)+3x^2(1-x) ai làm nhanh em cho trlhn ạ

Giải giùm mình đang cần gấp lắm cảm ơn mn rất nhiều

II.Write conditional sentences according to the ideas suggested: 1.Mary doesn’t see the sight. She can’t tell you about that. --------------------------------------------------------------------------------------- --2.It wasn’t fine yesterday. We didn’t go for a walk. ---------------------------------------------------------------------------------------------- 3.I saw it with my own eyes. I believed it. ---------------------------------------------------------------------------------------------- 4.The accident happened because the driver didn’t see the stop sign. ---------------------------------------------------------------------------------------------- 5.You can’t come late or they won’t let you in. --------------------------------------------------------------------------------------------- -6.I don’t know Greek, so I can’t tell you about that. --------------------------------------------------------------------------------------------- -7.Gravity keeps people from being hurled off the earth as it whirls around. --------------------------------------------------------------------------------------------- -8.Stop talking or you won’t understand the lesson. --------------------------------------------------------------------------------------------- -9.The church bells keep me from sleeping. ---------------------------------------------------------------------------------------------- 10.Go right now or you’ll be late for the train. ---------------------------------------------------------------------------------------------- 80. We must take steps to preserve natural resources, or the planet will be in danger.  Unless…………………………………………… 81. It’s such a pity your sister can’t come as well.  If only…………………………………………… 82. The soil would become poor unless the farmer added fertilizers.  If …………………………………………… 83. You probably won’t have time, but I’d like you to come and see.  If …………………………………………… 84. There were such a lot of traffic; that’s why we are late.  Had…………………………………………… 85. I couldn’t have managed it without your help.  If_…………………………………………… 86. It was her determination which enable her to get better so quickly.  If…………………………………………… 87. He doesn’t get a job, so he can’t pay his bills.  If…………………………………………… 88. She isn’t fit because she sits around too much.  If…………………………………………… 89. The fire brigade came immediately, so the house didn’t burn down.  If_…………………………………………… 90. Sue walked to work in the rain and caught a cold. If…………………………………………… 91. We can’t bathe in this part of river because the water is too dirty. …………………….………………………………………………………… 92. We spend too much money on electricity because we have four air conditioners in our house. ……………………….……………………………………………………… 93. I can’t write to Linh because I don’t have her address. ……………………….……………………………………………………… 94. Dick often causes accidents because he drives carelessly. ……………………….……………………………………………………… 95. We can’t give much help to the poor because we waste a lot of money on unnecessary things. ……………………….……………………………………………………… 96. Without this treatment, the patient would have died.  If he …………………………………………… 97. We got lost because we didn’t have a map. If we …………………………………………… V : Rewrite the following sentences using “Unless” 1. I won’t go to school if I don’t feel better. …………………………………………… 2. Tony will talk to you if you question him. …………………………………………… 3. If you don’t put on your overcoat, you’ll be cold. …………………………………………… 4. You will fail the exam if you don’t work hard. …………………………………………… 5. You’ll get a cold if you don’t keep your feet dry. …………………………………………… 6. If I don’t leave now, I’ll miss my flight. …………………………………………… 7. If you aren’t going to the party, I won’t go. …………………………………………… 8. I can’t send you a postcard if you don’t give me your address. …………………………………………… 9. If I won a big prize in a lottery, I’d build a school for the poor. …………………………………………… 10. I’ll call the police if you don’t leave me alone. ……………………………………………

Giải giúp mình 25 đến 30 với ạ gấp :(

Cho đường tròn (O) có bán kính OA và OB. Trên cung nhỏ AB lấy các điểm M và N sao cho AM = BN.Gọi C là giao điểm của các đường thẳng AM và DN Chứng minh: a) OC là tia phân giác của góc ACB b) OC vuông góc AB

giúp nhanh hộ e vs ạ (Ko cần giải thích) e cần gấp lắm ai xg trc e sẽ vote 5* + 1 cảm ơn nhé Câu 2 : Một hình chữ nhật có chiều dài gấp 3 lần chiều rộng được mở rộng về hai phía, một phía chiều dài và một phía chiều rộng mỗi chiều 2 m. Hình chữ nhật mới có diện tích lớn hơn diện tích hình chữ nhật cũ là 84 m2. Tính diện tích hình chữ nhật ban đầu?